<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
var isUnique = function(astr) {
    for( var i = 0 ; i<astr.length ; i++ ){
        for( var k = i+1 ; k<astr.length ; k++ ){
            if( astr[i] == astr[k] ){
                return false
            }
        }
    }
    return true
};

var astr = 'leetcode'
console.log(isUnique(astr))
    </script>
</body>
</html>